电脑计算机编程入门教程自学编程语言_怎么利用MurmurHash算法缩短网址缩短?

uint32_t murmur3_32( const uint8_t* key, size_t len, uint32_t seed )

{

    uint32_t h = seed;

    if ( len > 3 )

    {

        const uint32_t    * key_x4    = (const uint32_t *) key;

        size_t        i        = len >> 2;

        do

        {

            uint32_t k = *key_x4++;

            k    *= 0xcc9e2d51;

            k    = (k << 15) | (k >> 17);

            k    *= 0x1b873593;

            h    ^= k;

            h    = (h << 13) | (h >> 19);

            h    = (h * 5) + 0xe6546b64;

        }

        while ( --i );

        key = (const uint8_t *) key_x4;

    }

    if ( len & 3 )

    {

        size_t        i    = len & 3;

        uint32_t    k    = 0;

        key = &key[i - 1];

        do

        {

            k    <<= 8;

            k    |= *key--;

        }

        while ( --i );

        k    *= 0xcc9e2d51;

        k    = (k << 15) | (k >> 17);

        k    *= 0x1b873593;

        h    ^= k;

    }

    h    ^= len;

    h    ^= h >> 16;

    h    *= 0x85ebca6b;

    h    ^= h >> 13;

    h    *= 0xc2b2ae35;

    h    ^= h >> 16;

    return(h);

}